OK heres the deal..im gonna answer all ur Q's... Si (maybee the S did too) had the tweeter option...they came with it only if u opted for the premium sound system which came in different varieties. My 92 Si had the tweets and a Honda CD deck and tape deck. The stock tweets are 1". The way they are mounted is this. There should be a bracket in there. Put the tweeter inbetween the bracket and the back of the cover and secure it with a screw. There should be a hole in the bracket for this. This is the easiest speaker install in the lude.

If i left any part of the explanation unclear...i can make it clear for you with further explanation. I can provide pics if u really really want me to.